Beyond-the-Horizon Cruise Missile Defense Demonstration

JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 18, NUMBER 4 (1997) 501
MOUNTAIN TOP: BEYOND-THE-HORIZON CRUISE MISSILE DEFENSE
T
Mountain Top: Beyond-the-Horizon Cruise Missile
Defense
William H. Zinger and Jerry A. Krill
he Cruise Missile Defense Advanced Concept Technology Demonstration,
known as Mountain Top, was successfully completed at Kauai, Hawaii, during January
and February 1996. The demonstration featured a new type of cooperative engagement
known as “forward pass,” made possible by the Cooperative Engagement Capability, in
which low-flying drones were engaged beyond the horizon of an Aegis ship for greatly
increased engagement range. Although the Navy performed the forward pass
cooperative engagements alone, the Marine Corps, Air Force, and Army participated
in other major joint-services exercises. Most significantly, the concept of a surface-
launched, air-supported engagement of cruise missiles was validated and has provided
the impetus for follow-on joint-services pursuit of an extended, beyond-the-horizon
engagement capability for defense of land sites from land-, air-, and sea-based missile
defense systems. This article describes the background, objectives, conduct, and results
of the Mountain Top test operations. Also detailed are the systems engineering
concepts, system configurations, and the test and evaluation process that went into the
planning, conduct, and analysis of the many complex experiments of the Advanced
Concept Technology Demonstration.
(Keywords: Beyond the horizon, Cooperative engagement, Forward pass, Joint services,
Mountain Top, Overland cruise missile defense.)
BACKGROUND
The concept of intercepting low-flying targets by
ship-launched missiles beyond the ship’s horizon with
the aid of an airborne platform was considered over two
decades ago. By removing the limitation of the ship’s
radar horizon, such a concept envisioned the intercep-
tion of targets much farther from the defended and
engaging units, allowing time for additional engage-
ments if necessary. Figure 1 illustrates the evolution of
the “forward pass” concept.
The earliest version of the concept, examined at
APL in the mid-1970s as part of the Battle Group Anti-
Air Warfare Coordination Program, embodied prima-
rily the element of beyond-the-horizon guidance. In
this case, a Standard Missile (SM) would be directed
via the ship’s missile midcourse control link to the
vicinity of an F-14 fighter. The fighter’s fire control
radar, modified for this role, would illuminate the tar-
get, allowing the missile to home on the reflected il-
lumination from the target.
A modified form of forward pass emerged in the late
1970s to early 1980s during a series of “outer air battle”
studies, which addressed next-generation Navy battle
group air defense requirements against Soviet bombers
armed with long-range antiship cruise missiles. If the
bombers could be intercepted before they approached
to within range of launching their missiles at U.S.
TECHNOLOGY DEMONSTRATION

W. H. ZINGER AND J. A. KRILL
502 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 18, NUMBER 4 (1997)
ships, a critical new layer of defense would be provided.
This variant of forward pass featured a conceptual, long-
range ramjet missile that could be launched from an
Aegis cruiser and flown toward a carrier-based surveil-
lance and fire control aircraft. The aircraft would carry
advanced, long-range sensors to detect bombers and to
take over midcourse missile control from the ship via
an onboard aircraft-to-missile link. The missile was
envisioned to have a multisensor homing seeker capable
of locking onto a target from long distances. This form
of the concept (Fig. 1, center) was known as “midcourse
handover” in contrast to the “remote illumination”
approach of the F-14 concept. From these outer air
battle studies, in which APL was a prominent partic-
ipant, a requirement for a long-range form of SM (now
known as SM-2 Block IV) emerged along with the need
for a “cooperative engagement link.”
The Laboratory participated in yet another series of
related studies in the mid- to late 1980s, centered
around the use of an airship to carry weapon system
elements comparable in function to the phased array
radar and illuminators of an Aegis cruiser, but with
reduced weight and new features for missile control.
Key among those features was the use of a “multifunc-
tion” phased array system as both the fire control radar
and illuminator. This feature provided multiplexed il-
lumination of targets, thus allowing simultaneous hom-
ing of several SM-2 missiles. Analysis showed that,
given sufficient equipment weight reduction and power
capacity, an airship so equipped and operating at an
altitude of over 10,000 ft could greatly extend the
effective surveillance and engagement range against
low-altitude cruise missiles.
This last example of forward pass can be seen as a
hybrid between a remote-illumination forward pass and
a form of cooperative engagement then being designed
for the Cooperative Engagement Capability1
(CEC; see
the boxed insert) known as engagement on remote data
(EOR). An EOR capability allows a ship to fire an SM-
2 missile and direct the missile midcourse and terminal
homing illumination using data from remote rather than
own-ship sensors. For this concept, the airship would
serve as both the remote data source for EOR and as the
remote homing illuminator in the forward pass mode.
This became the form of cooperative engagement con-
sidered for the eventual Mountain Top tests.
With the end of the Cold War and the advent of
littoral environment scenarios, the low-altitude cruise
missile threat became even more important, so that a
beyond-the-horizon intercept capability remained very
attractive. A variety of air platform candidates emerged
including large tethered aerostats, wide-body aircraft,
and a network of sensors from multiple smaller
(manned or unmanned) aircraft linked via the CEC.
An example of a concept using ship-launched aircraft
networked with CEC is shown in Fig. 2.
MOUNTAIN TOP
Demonstration
The potential operational advantages of a forward
pass capability led senior Navy and DoD officials to
conclude in 1993 that the likely payoff of an airborne
unit to extend surface-launched missile engagement
range was sufficiently compelling to explore as the
initial stage of an Advanced Concept Technology
Demonstration (ACTD). This ACTD stage eventually
featured two sets of test operations, which are described
in detail later in this article.
• Set1comprisedbeyond-the-horizonNavytests(Phase
1) and Army tests (Phase 2).
• Set 2, known as Enhanced Scenarios, involved par-
ticipation of the Navy, Marine Corps, Army, and Air
Force in joint exercises: arrival on the scene (Phase
1),defenseagainstshore-basedattacks(Phase2),and
joint littoral operations (Phase 3).
The organizations and participants in the ACTD are
presented in Table 1. (The boxed insert, APL Moun-
tain Top Team, lists the Laboratory personnel who
participated in the formal testing.)
Mid-1970s Mid- to late 1980sLate 1970s to early 1980s
Figure 1. Evolution of the forward pass concept, i.e., the concept of intercepting missiles attacking from beyond a ship’s horizon with the
aid of airborne radars: in the mid-1970s, aircraft illumination of the target for missile semiactive homing; from the late 1970s to early 1980s,
aircraft detection of the target and guided missile midcourse to multimode homing; by the mid- to late 1980s, aircraft detection of the target
and guided missile midcourse, and illumination of the target for pulsed semiactive missile homing.

Figure 2. Illustration of the land-attack cruise missile defense concept in which aircraft are networked via the Cooperative Engagement
Capability to form a composite airborne surveillance and fire control radar/terminal illuminator capability. This allows sea- and land-based
units to send an intercepting missile beyond the firing unit’s horizon. Engagement is thus possible at unprecedented ranges, thereby
providing extended defense against land-attack cruise missiles.
Table 1. Major players in the Mountain Top ACTD.a
Participant/organization Function
Navy CEC Program Manager ACTD program management
Office of Naval Research Acting sponsor
APL and MIT Lincoln Labs Lead laboratories
APL Technical Direction Agent
for CEC and SM-2
Raytheon E-Systems CEC prime contractor
Lockheed Martin Aegis prime contractor
Hughes Aircraft Co. SM-2 prime contractor
Naval Weapons Support Center Equipment and site support
Naval Sea Systems Command Tartar fire control radar support
Pacific Missile Range Facility Range operations support
a
Aegis and Standard Missile program offices also participated.
Patriot
battery
Track/
illuminate
Search
Search
Aegis
ship
Aegis/Standard Missile-2
midcourse
uplink/downlink
Cue
Patriot
missile
Standard
Missile

THE COOPERATIVE ENGAGEMENT CAPABILITY
The Cooperative Engagement Capability (CEC) has
been developed to network sensors and weapon systems in
a manner that allows a set of geographically diverse air
defense systems of various types to operate as if they were
a single entity, but with performance advantages that accrue
from the exploitation of their intrinsic diversities (i.e.,
locations and sensor characteristics). A full description of
CEC is available in a previous issue of the Technical Digest.1
For the convenience of the reader, the primary CEC char-
acteristics are briefly summarized here.
The CEC system consists of two subsystems: the Coop-
erative Engagement Processor (CEP) and a data transfer
element known as the Data Distribution System (DDS). In
Fig. A, the CEC is shown connected to the Aegis combat
system, for example. The CEP provides its combatant’s
weapon system with a composite track picture as well as
recommended target identity. This is accomplished by using
local and remote sensor measurements and information
friend or foe (IFF) responses, which are exchanged via the
DDS, to create a common air picture that is more complete
and more accurate than one obtained from the best con-
tributing sensor. With this quality information, a unit may
engage using only remote data, even if the target is fast and
maneuvering. The DDS performs the networking functions
of automatically establishing and maintaining a secure net-
work for rapid exchange of target position measurements
and associated data messages among all cooperating com-
batants.
The CEP on a given combatant is interfaced to its prin-
cipal sensors, from which it receives radar or IFF target
reports and to which it provides data for special acquisition
or gating to acquire targets not locally held. All sensor or
IFF reports associated with each assigned track are ex-
changed via the DDS with other cooperating units. The
exchanged data include, as appropriate, target range, bear-
ing, elevation, Doppler (if available), sensor type, and as-
sociated track number. Unit position data obtained from
inertial navigation data, DDS-to-DDS measurements, and
other pertinent sources are also exchanged. The CEP grid-
lock function computes the precise relative positions of
cooperating units and calibrates sensor angular and range
alignments by correlating reported positions of common,
multiply tracked targets.
Using these data, the CEP develops an optimized com-
posite track of each target by applying a quality-weighted
combination of all data sources via a Kalman filter. Con-
tinual tests for target splits and merges are made at the
measurement input level. These track data are provided to
the combatant’s weapon system for fire control use and to
its command/control element. The exchange and process-
ing of unprocessed target measurement data—rather than
the exchange of track data (with its inevitable lags and
corruption by fades), as is common to tactical link net-
works—is a key feature of the CEC concept and is respon-
sible for its ability to generate fire control–quality data for
sensor/weapon acquisition and missile guidance.
The CEP also exchanges engagement status data among
cooperating weapon systems. In the future, it will compute
the relative engageability of undesignated targets by the
various weapon systems for recommendation of weapons
engagement assignments among networked units.
DDS elements, using their directive phased array an-
tennas, automatically establish and maintain a communi-
cation network among all cooperating units by synchro-
nously switching their transmit and receive beams among
pairs of units in parallel (Fig. B). Because each DDS pos-
sesses a phased array with a single beam for either trans-
mission or reception, each unit can only point its beam to
connect (transmit or receive) to one other DDS at a time.
Each connection event involves one unit transmitting
through its beam to another unit and the other unit point-
ing its beam at the transmitting unit to receive from it. This
transmit/receive beam connectivity is generally performed
in parallel among pairs in the network at precise times via
the DDS cesium clocks using a common, adaptive algo-
rithm. Different pairings occur every “frame,” a small sub-
second block of time. If a connectivity path or a unit is lost
CEC
Weapon
control
system
SPY-1B
radar
IFF CEP
DDS
Command/
decision
Displays
Command/
control links
SPS-49
radar
Figure A. CEC interfaces to the Aegis combat system.
Objectives
The Mountain Top ACTD management plan2
iden-
tified the Navy, Army, and the Advanced Research
Projects Agency (ARPA) as the primary participants
and was approved by senior Army, Navy, DoD, and
Ballistic Missile Defense Organization officials.
The objective of . . . (Mountain Top) is to demon-
strate the potential for significant enhancements to air
defense capabilities by integrating Navy/Army/ARPA
technology developments and existing air defense sys-
tems. The goal is to detect, track, and successfully engage
cruise missiles at ranges beyond the radar line of sight
of surface-based air defense units, and provide an oppor-
tunity to assess joint doctrine and concepts of air defense
operation.2
Toward this objective the plan required an explora-
tion of three new capabilities2
:

(e.g., because of equipment failure, excess jamming, or
propagation fade), the loss of connectivity is communicat-
ed throughout the network, and the common algorithms
adjust the schedules and any relay sequences identically
and automatically at each DDS.
Antenna directivity and relatively high transmitter pow-
er provide the required countermeasures immunity and
margin against propagation fading, while maintaining a high
data rate and a low error rate. The phased array design
permits the near-instantaneous beam pointing necessary to
meet stringent subsecond timing requirements associated
with sensor measurements. The utilization of a narrowbeam-
directed phased array antenna for both transmission and
reception is unprecedented for a mobile communication
system, as is the unique scheduling and control process used
by the DDS.
Transmit
Transmit
Receive
Receive
Time frame N + 1
Transmit
Transmit
Receive
Receive
Time frame N + 3
Transmit
Receive
Receive Transmit
Time frame N + 2
Time frame N
Transmit
Receive
Transmit
Receive
Because of these characteristics, the CEC provides the
weapon system on every cooperating combatant with a
composite track picture that is more precise and contains
more rapidly updated target data than any individual con-
tributing sensor. This is accomplished by the use of a sophis-
ticated Kalman filter and the data flow logic of multiple
sensor data, which exploit the more accurate range-versus-
bearing data (for radars), eliminate target fades due to mul-
tipath and refraction fades (especially over land), circum-
vent main-beam jamming and local clutter, and utilize fa-
vorable target aspect. In the case of elevated sensors, as in
the Mountain Top tests, the composite track also overcomes
the horizon limitations of own-ship radar for the firing unit.
In addition, CEC obtains a force-wide assessment of target
identity and engageability, greatly enhancing the cumula-
tive effectiveness of the force.
Figure B. DDS directive pair-wise operation.
1. Increased target acquisition and tracking ranges (be-
yond radar horizons) and extended target terminal
illumination ranges through elevated sensor suites
2. Sensor networking along with a high data rate and
fire control–quality data
3. Increased target engagement ranges
Measures of effectiveness for the Navy included
target detection and firm track ranges, fire control
connectivity between an elevated site and the ship,
missile intercept range beyond the ship’s horizon
from the ship, inbound and crossing target trajectories
relative to the ship, and low target altitude above the

sea surface at sub-Mach speed. A key purpose of the
ACTD, then, would be to validate the physics embed-
ded in the forward pass concept and the performance
characteristics of the equipment so that the results
could be confidently applied to tactically oriented
system development.
Installations
Many considerations went into the planning, con-
duct, and evaluation of the Mountain Top ACTD. In
support of the demonstration, APL, in collaboration
with Massachusetts Institute of Technology Lincoln
Labs, proposed the following: Since available fire con-
trol radar and illuminator elements were too heavy to
be carried by air vehicles, a mountaintop could be used
as a surrogate aircraft. This would allow existing ship
and prototype aircraft equipment to be installed on an
elevated site to emulate future airborne elements and
functions.
A mountain site on the island of Kauai, Hawaii
(Kokee Park), near the Pacific Missile Range Facility
(PMRF) at Barking Sands, met all the foreseen require-
ments. This site had three advantage: steepness, exist-
ing government installations near the coast, and deep
water in which ships could operate safely near shore.
APL MOUNTAIN TOP TEAM
The following APL staff and resident subcontractors (listed alphabetically) participated in the formal Mountain Top testing
during January and February 1996. The list illustrates the breadth and depth of the Laboratory’s involvement in those events.
CEC design, integration (land/ships/
aircraft), test data evaluation
G. P. Allyn
A. D. Bernard
J. M. Davis
G. P. Gafke
R. W. Garret
S. F. Haase
H. H. Hamilton
L. M. Hubbs
S. A. Kuncl
S. Kuo
G. K. Lee
D. J. Levine
R. E. Martinaitis
T. A. McCarty
R. C. McKenzie
C. L. Myers
J. R. Pence
R. W. Proue
C. P. Richards
D. B. Schepleng
M. Y. Shen
L. W. Shroyer
V. I. Stetser
J. W. Stevens
O. M. Stewart
D. M. Sunday
P. H. Temkin
D. I. Tewell
T. T. Tran
G. C. Uecker
C. Vandervest
L. A. Ventimiglia
J. Wong
C. A. Wright
Critical experiments, data collection,
special instrumentation
(some experiments were performed prior to
January/February 1996)
R. A. Beseke
A. J. Bric
M. H. Chen
S. J. Crosby
G. J. Dobek
G. D. Dockery
W. P. Gannon
W. R. Geller
J. Goldhirsh
J. M. Hanson
A. S. Hughes
R. Z. Jones
B. E. Kluga
F. J. Marcotte
J. H. Meyer
J. J. Miller
C. P. Mrazek
P. D. Nacci
J. R. Rowland
R. C. Schulze
R. M. Waterworth
L. H. White
Documentation/photography
G. A. Boltz
J. G. Fiske
R. L. Goldberg
R. E. Hall
J. E. O’Brien
Program management/liaison
C. J. Grant
R. T. Lundy
M. Montoya
S. M. Parker
J. E. Whitely
Senior management
R. W. Constantine
M. E. Oliver
G. L. Smith
W. H. Zinger
Site design/installation support
L. J. Adams
R. Barry
D. J. Buscher
C. A. Daly
H. F. Dirks
P. N. Garner
D. E. Johnson
M. H. Luesse
L. E. McKenzie
M. L. Miller
Systems engineering
W. I. Citrin
J. A. Krill
P. E. Lakomy
J. R. Moore
J. F. Rediske
D. D. Richards
R. E. Thurber
Test preparation, coordination,
conduct
C. R. Cook
A. F. Jeyes
G. Long
M. R. Sands
R. D. Timm
N. E. White

The Kokee Park Site A, situated 3800 ft above sea
level, was an abandoned NASA installation. The Navy
had to establish appropriate electrical services, repair
and upgrade the laboratory facilities, and erect special
towers to support the radars and CEC (Fig. 3), while
meeting the environmental standards of this famous
state park. Kokee also served APL and E-Systems as the
primary engineering data analysis site for the CEC
network and as the base of operation for the radar
agents, MIT, and the Naval Sea Systems Command.
Aegis and SM-2 data analyses were performed by Lock-
heed Martin and the Navy at Barking Sands. APL, in
collaboration with the Navy, established data lines to
the primary test conduct and control site at Barking
Sands to make the composite CEC track data output
available for test control.
The 1700-ft-elevation Makaha Ridge site, equipped
with the AN/SPS-48E (hereafter, SPS-48E) surveil-
lance radar and IFF (information friend or foe), was
integrated into the Kokee CEC system via fiber-optic
lines. This enabled the elevated sites to more accurate-
ly resemble the full avionics suite of the elevated fire
control/surveillance aircraft concept, which would be
expected to provide a multiple-target tracking and IFF
capability. The integration scheme complemented the
single-target tracking radar and fire control radar ele-
ments at Kokee and provided for multiple mutual tar-
gets with the SPY-1B radar of an Aegis cruiser for CEC
precision gridlock (these and other defense units are
described in the next section).
To provide a ready surrogate “link” between CEC
and the Army Patriot unit, Joint Tactical Information
Distribution System (JTIDS) terminals were installed at
both the Kokee and Barking Sands sites, i.e., at Kokee
the JTIDS was indirectly connected to the CEC display
interface via a device developed by the Naval Space and
Air Warfare Command, and at Barking Sands the ter-
minal was connected to an existing Patriot interface.
The airport at Barking Sands supported a commercial
helicopter equipped with APL-developed atmospheric
sensors,3,4
the Captive Seeker Lear aircraft (discussed
below), and the P-3 aircraft used in the Enhanced
Scenarios. Both the Makaha Ridge site and an aerostat
tethered at Barking Sands were equipped with special
infrared sensors to provide insight into potential coop-
erative, networked infrared systems for longer-range de-
tection of low-flying targets.
Before describing the actual test operations, the
technical foundation upon which the Mountain Top
results were based is described in the following section.
TECHNICAL FOUNDATION
System Elements
The weapon system elements participating in the
Mountain Top beyond-the-horizon ACTD (Set 1) are
presented in Table 2; Table 3 lists additional elements
participating in the Enhanced Scenarios (Set 2). The
following paragraphs briefly describe the characteristics
of the CEC-networked weapon
system elements.
CEC: Sensor and Fire Control
Network
As noted in the boxed insert, the
CEC was developed to allow a net-
work of air defense units to inte-
grate their collective sensor mea-
surement and weapons control data
so as to operate as a single, distrib-
uted air defense system. For the
ACTD, two specially adapted CEC
equipment sets were built, one for
the Kokee surrogate aircraft site
and the other for the USS Lake Erie
(Aegis CG 70). The CEC electron-
ics differed somewhat from the
permanent ship sets installed on
the USS Anzio and Cape St. George
(Aegis CG 68 and 71, respectively)
to reduce weight and facilitate
housing in a shelter. A follow-on
cruise missile defense (CMD) phase
Figure 3. Kokee Park “surrogate” aircraft site A, at a 3800-ft elevation. In addition to
providing the surrogate forward pass aircraft functions, test data evaluation of the site
elements and the CEC was conducted here. The system elements are described in the text.
RSTER
roto-dome array
CEC array antenna
MK 74 fire control radar
and illuminator area
Kokee site A
engineering test evaluation and
surrogate avionics facility

Table 2. Major beyond-the-horizon test elements (Set 1).
Element Type Function
Radar surveillance Pulsed Doppler array Stationed at elevated sight to perform target
technology experimental radar surveillance
radar (RSTER)
Mark 74 (MK 74) Tartar fire control radar Stationed at elevated site to provide precision
target data and target illumination
SPS-48E Terrier New-Threat-Upgrade Stationed at elevated site to provide
three-dimensional radar surveillance and gridlock data
CEC Cooperative engagement/ Networked radars and illumination to weapon
sensor network control for composite track picture and
cooperative engagement
USS Lake Erie Aegis, CG 70 Provided engagement control and missile
launch/guidance
SM-2 Block IIIA Guided missile Responded in-flight to midcourse
(instrumented) commands and performed semi-active
homing and warhead fusing
BQM-74 Drone Controlled from elevated sight; flown with
characteristics of a low-altitude attacker
Table 3. Major additional elements used in the Enhanced Scenarios (Set 2).
Element Type Function
USS Anzio and Cape St. George Aegis, CG 68 and 71 Varied depending on scenario, including
(with CEC) data collection and cooperative
SM-2 engagements
Hawk Marine Corps anti-air Provided engagement control and missile
weapon system launch/guidanceforHawkmissilefirings
TPS-59 Hawk radar Provided elevated surveillance
Aerostat Tethered, unmanned airship Supplied elevated digital communication
relay for Hawk firings and infrared
sensor test vehicle
AWACS Air Force airborne warning Collected surveillace radar data and
and control system reported tracks over JTIDS
P-3 U.S. Customs Service surveil- Served as part of the CEC net with
lance aircraft (with CEC) surveillance radar
Patriot Army surface-to-air Collected radar data; reported
missile system tracks over JTIDS
BQM-74/-37 Target drones Served as SM-2 and Hawk firing
scenario targets
JTIDS Link 16 Tactical data link Provided command/control link
F-15/F-16 Air Force and Air Served as scenario red and blue forces
Reserve fighters
Big Crow and Q-Lear Electronic warfare test aircraft Served as electronic warfare threats
(jammers)

is being planned, which will feature a next-generation
preproduction E-2C version of the CEC equipment
called the “common equipment set.” This set has iden-
tical electronics for surface and air units, yet conforms
to the more constrained airborne payload. Reference 1
discusses the differences between these versions.
Functionally, the CEC for this demonstration was a
derivative of the version used during 1994 develop-
ment testing2
with the addition of hardware and soft-
ware for interfacing with radar surveillance technology
experimental radar (RSTER) and the Mark (MK) 74
tracking illuminator.
RSTER: Advanced Airborne Surveillance Radar
RSTER was developed for ARPA by MIT Lincoln
Labs to evaluate experimental Doppler radar technol-
ogies. For this demonstration, RSTER was installed at
the Kokee site to provide the required horizon detec-
tion range performance and was fitted with a prototype
advanced E-2C phased array antenna in a “roto-dome”
configuration. The system search and track software
was also modified by MIT for the ACTD to significant-
ly increase the update rate, so as to minimize track filter
lag errors due to target maneuvers and to ensure earlier
detection through shorter search frame times.
Aegis: Air Defense and Combat System
Aegis ships were the primary air defense forces in
most Mountain Top scenarios. The Aegis air defense
weapon system uses the multifunctional SPY-1B phased
array radar to perform the search, track, and fire control
functions. The CEC-integrated version of the Aegis
weapon system that was a derivative of the Baseline 4
computer programs1
was used with minor modifications
to meet ACTD requirements. This version had been
demonstrated to enable the Aegis system to perform an
SM-2 engagement on a target, even when the firing
ship’s SPY-1B radar did not track the target, by using
fire control radar data from another ship via CEC. This
type of cooperative engagement, i.e., EOR, was de-
scribed earlier in this article.
Tartar MK 74: Surrogate Airborne Fire Control
Tracking Radar and Illuminator
The Aegis system with CEC had already been
modified to accept remote fire control radar data from
either another Aegis radar or from a fire control radar
on Tartar New-Threat-Upgrade (NTU) ships that sup-
port a different version of SM-2.1
For testing in 1994,
the Tartar system had also been integrated with CEC
and was able to meet the engagement range objectives
of the management plan with remote data, serving as
either a source or a firing unit.1
For this ACTD, the
Tartar MK 74 missile fire control system installed at the
Kokee site served as both the fire control radar source
and the terminal homing illuminator for the Aegis SM-
2, in the same manner as it serves as both radar and
illuminator on a Tartar ship for a Tartar configuration
of SM-2. Modeling indicated that the MK 74 met the
required fire control radar detection range and had
sufficient illumination power for a modified SM-2
missile to achieve the intercept range well beyond the
ship horizon, even if the ship was 25 nmi forward of
the illuminator. Relatively minor changes were made
to this element, mainly to make it compatible with
RSTER cueing accuracy and with negative, look-down
target elevation angles (owing to its mountain altitude
relative to the horizon). Figure 3 shows the MK 74
system, RSTER, and CEC antenna as part of the Kokee
site installation.
SM-2 Block IIIA with Experimental Modifications
The latest-generation SM-2 in the Fleet is the Block
IIIA, which, like Block III, has exhibited a very high
intercept success rate. As will be noted in the next
section, a beyond-the-horizon geometry and an elevat-
ed illuminator produce much greater sea reflection
than seen in normal low-altitude engagements. There-
fore, to reduce clutter interference, Hughes Aircraft
modified the IIIA seeker by incorporating the “Plate 1
receiver upgrade” under development for the next-
generation Block IV. The missiles were also furnished
with a telemetry package to transmit terminal homing
signals to determine intercept performance.
Systems Engineering Approach
The systems engineering process used to develop the
distributed Navy forward pass weapon control network
(consisting of Aegis/SM-2, CEC, and the mountaintop
radars and illuminator) entailed all participating orga-
nizations in extensive analysis, experimentation, and
planning extending over a 30-month period. Figure 4
shows this process as it applied to Mountain Top. Be-
cause of the diversity of program offices involved, each
with their respective engineering teams, a systems en-
gineering working group was formed under the coordi-
nation of the CEC program to ensure that design and
interface issues were identified and resolved as the prin-
cipals proceeded to design, review, and document the
networked system. Issues included the ship and missile
launch safety zone requirements for the PMRF range,
types of drones, availability of systems (such as the
versions of SM, Aegis ship combat system, and moun-
taintop illuminator), and the local geological features.

The primary system models and simulations that
have been used through the years by the various
programs were adapted to this effort. Because the
models had been previously validated with test data
and broadly used, the systems engineering team had
much confidence in them. As will be discussed later in
this article, test results were very close to the model
predictions.
Since CEC provided the means to effect the
ACTD’s “distributed weapon system,” the role of APL’s
Technical Direction Agent (TDA) extended to tech-
nical coordination in carrying forward the netted sys-
tems engineering process. Since the Laboratory is also
the TDA for the SM-2 and Tartar NTU programs, and
serves as technical advisor to the Aegis program as well,
it was involved on both sides of the CEC interfaces.
Analysis
Analysis prior to the Mountain Top demonstration
showed that
• Sensorsandfirecontrolcouldprovideadequaterange
performanceagainstthespectrumofatmosphericand
sea conditions experienced around Kauai.
• CEC network and missile error budgets would permit
midcourse guidance with acceptable errors for a suc-
cessful terminal homing phase.
• Missile seeker pointing errors at the start of terminal
acquisition were sufficiently small to support target
acquisition.
• The Block IIIA version of SM-2 possessed sufficient
kinematics to support stable flight and terminal con-
trol at the ranges and altitudes of interest.
• The Block IIIA would be able to acquire and track a
drone-sized target in the expected sea clutter back-
ground if modified with the Plate 1 upgrade to sup-
press clutter interference.
Missile Captive Seeker Critical Experiments
In the course of the SM development program, APL
had performed critical Captive Seeker5
experiments for
ACTD management plan
top-level requirements
Interface specifications
Functional/performance
allocations
Critical experiments and modeling
Fabrication/modification Integration tests
Site and
preparatory tests
Formal ACTD tests
Figure 4. The systems engineering process as applied to the Mountain Top ACTD, beginning with the concept and requirements
definition, proceeding through requirements allocation to the elemental level, and finally to testing from the smallest elements up to the
fully networked composite system. APL provided leadership in modeling, requirements definition and allocation, interface specifications,
critical experiments, site risk reduction scenarios, site subsystem checkout and verification, and test conduct. Shown in the formal ACTD
test inset, from right to left, are APL’s Test Conductor, Art Jeyes, sitting beside the CEC and Mountain Top Program Manager, Michael
O’Driscoll, and RADM Timothy Hood, the Program Executive Officer for Theater Air Defense.

a variety of sea- and land-clutter conditions to deter-
mine the effects on seeker performance against low-
flying targets. These experiments showed that, based
on Mountain Top geometry, steeper illumination inci-
dence angle to the sea, longer range, higher surface
reflection, and different Doppler characteristics, the
missile receiver would require special filtering com-
pared with a conventional engagement. The Plate 1
upgrade had already been developed for the longer-
range Block IV missile, and performance modeling
indicated that it would also suffice to allow the Block
IIIA seeker to distinguish the illumination reflection
from the target relative to that from the sea surface for
the Mountain Top geometry. However, only limited
experimental data existed to support this conclusion.
To capture the seasonal sea and atmospheric char-
acteristics to be encountered, the Captive Seeker
experiment was conducted about a year before the
ACTD. Another Captive Seeker test series was also
performed for the actual engagement geometries and
targets several months before the firing events. Both
sets of test results confirmed that Block IIIA, modified
with the Plate 1 clutter filter, would be effective under
Mountain Top conditions.
Radar Experiments
The foregoing analysis and systems engineering ef-
forts were augmented by risk reduction assessments and
other critical experiments for key aspects of the dem-
onstration, e.g.,
• Theacquisition,track,andilluminatorpowerdensity
of the MK 74 system were examined for the geometry
of each of the planned beyond-the-horizon en-
gagement scenarios using the Captive Seeker system
against drones.
• TheacquisitionandtrackperformanceoftheRSTER
radar was tested for the geometry of each planned
engagement.
• The modifications required to the Aegis combat
system were analyzed, defined, and then tested at the
Aegis combat system engineering development site.
Test and Evaluation Process
Test Engineering
As a complement to the systems engineering pro-
cess, a test and evaluation working group was formed
early in the Mountain Top preparation effort. The
group worked out such issues as
• Impact on engagement range due to range safety
requirements
• Selection of the Kauai mountain ridge with sufficient
height to achieve required range to the target horizon
• Hawaiian state park environmental requirements for
visual, electromagnetic, and acoustic noise effects
• PMRF requirements to provide drone control out to
the required ranges (resulting in the development
of a new long-range drone control system for this
purpose)
• Selection and preparations of the BQM-74 drones
with the requisite characteristics
Scenarios were defined in terms of inbound trajec-
tories and engagement geometries in accordance with
the systems engineering design, and were embodied in
a series of test and evaluation planning documents
(e.g., Mountain Top installation plan and installation
documents, PMRF plan, requests for test assets, test
plan and procedures, and data evaluation plan). The
Navy Program Office directed APL to conduct the test
series.
Test Planning
The next level of detailed preparations included
scheduling site preparations, ship installations, test
support assets, and test range services as well as assess-
ing ship availability requirements for checkout, re-
hearsal, and test. Testing began at the subsystem level,
for example, starting with the SPY-1B computer pro-
gram and the CEC processor modules, proceeding
through interface tests, and finally testing the entire
CEC network of systems (Fig. 4). These tests were
performed at the sites of the design agents (see Table
1). Interface tests were generally performed between
CEC and weapon system elements at the combat sys-
tem test sites using APL-supplied wrap-around simula-
tors. Finally, network-level tests were performed at
PMRF. Key decision points for the higher-level events
were formal test readiness and control panel reviews,
missile firing scenario certification review, and a weap-
on safety review. The final reviews were chaired by
senior Navy officers.
BEYOND-THE-HORIZON TESTS
Phase 1: Navy Firing Tests
The Navy tests consisted of a series of firing exer-
cises by an Aegis ship (USS Lake Erie) against a low-
flying drone (BQM-74 representing a simulated enemy
target). Remote target radar data were used along with
illumination by radars mounted on the Kokee site radar
surrogate “aircraft.” The integration of the target data
from the elevated site into composite fire control–
quality tracks was accomplished by CEC. The test con-
figuration is illustrated in Fig. 5, which represents the
CMD concept shown in Fig. 2. Not shown is the SPS-
48E three-dimensional surveillance radar at the lower
Makaha Ridge site that provides target identification

and data to enable CEC to precisely gridlock the system
elements relative to one another.
Test Sequence
The sequence for each of the beyond-the-horizon
firing events was as follows (also see Fig. 6):
1. The CEC established gridlock (precise relative sensor
alignment and position of scenario elements) from
area targets seen by both the land site and ship. CEC
unitsatthelandsiteandshipperformed(independent
but identical) composite tracking and identification
from distributed radar and IFF data.
2. The BQM-74 drone was launched from the Barking
Sands site, flown outbound for 80 nmi, turned in-
bound, and descended to low altitude.
Kokee site
Aegis CG
missile initialization
and midcourse
Aegis/SM-2
midcourse
uplink/downlink
Standard
Missile
MK 74
CEC
Track/illuminate
Search/cue
Composite track
development
Barking
Sands
BQM-74
Patriot
radar
SPY-1B radar horizon
Joint Tactical
Informatiom
Distribution
System
RSTER
Figure 5. Conceptual representation of Mountain Top tests configured to represent the cruise missile defense concept depicted in Fig. 2.
Figure 6. Representation of the sequence of the initial beyond-
the-horizon engagement. The plan view indicates a low-elevation
inbound drone approaching the Kokee site with a crossing target
intercept by the ship-launched SM-2 (not drawn to scale).
Niihau Kauai
Pacific Missile
Range Facility
USS Lake Erie
Kokee Park
Barking Sands
Planned
intercept point
North/southrangerelativetoKokee
East/west range relative to Kokee

3. RSTERdetectedthedroneandpassedmeasurement
data to its land-site CEC. The CEC passed measure-
ments to the ship. Both CEC units (land and
ship) independently derived the track of the drone
target.
4. Aegis commanded the drone to be engaged. From the
engagement command, CEC cued MK 74 to acquire
the target. Both CEC units performed composite
tracking of the drone using RSTER and the more
accurate MK 74 data. CEC provided target measure-
ment data from the MK 74 to the ship.
5. TheshiplaunchedanSM-2missileatthetarget,then
guidedSM-2viaitsmidcourselinktowithinterminal
homing range using CEC target data for fire control.
6. The CEC commanded MK 74 to illuminate the
target. The ship commanded the missile to begin
homing. The missile intercepted the target.
Test Results
For the initial scenario event, the drone approached
a fictitious target on the beach, where it was intercept-
ed by the SM-2 well beyond the ship’s horizon and well
prior to the target area. The missile not only passed
within lethal range of the drone but scored a direct hit.
Figure 7 shows the composite track picture created by
an automated data reduction system based on CEC data
collected at the Kokee site. This was the first-ever
engagement of a low-altitude target beyond the firing
ship’s horizon.
The distributed missile control between the ship and
mountain site had been comparable in intercept per-
formance to the best that could be expected of conven-
tional, ship-only engagements, yet at a range many
times that possible by the cruiser against such a target
without the elevated elements. Furthermore, the
predicted SM-2 seeker characteristics, the detailed
models of detection and track performance of the
mountain sensors, and the simulated missile fly-out
predictions were very close to actual event results.
Another scenario event (Fig. 8) featured the drone
flying toward the ship and crossing relative to the is-
land mountaintop sensors. The missile made a success-
ful intercept and damaged the target. Again, the inter-
cept range was well beyond the firing ship’s horizon and
very close to model predictions.
The final forward pass scenario of this set of events
entailed aligning the drone approach path with the
ship and the mountain. Although the geometry was
simpler (i.e., the drone was inbound and not crossing
with regard to the ship and mountain site), detection
and engagement presented a greater challenge because
of predicted multipath propagation fading. However,
the missile again successfully intercepted the target.
The engagement range was close to the maximum that
modeling indicated to be achievable for the test con-
ditions and system elements used.
This final test highlighted an important feature of
the CEC design: When the ship first ordered an engage-
ment, causing the CEC to cue the MK 74 fire control
radar from RSTER data, the MK 74 could not acquire
the target because of a (predicted) multipath fade at
that range. The CEC unit on the mountain reported to
the ship CEC that the required remote data could not
be provided at that time. The ship operator, so alerted,
ordered the engagement again, by which time the drone
had flown out of the fade region, thereby enabling the
MK 74 to acquire and support the successful intercept.
These tests met and exceeded all objectives. All
three low-flying targets were successfully intercepted at
ranges well beyond those possible with a single ship.
The tests demonstrated the technical feasibility of
providing a Fleet-wide ability to defend inland targets
against low-flying cruise missiles using special aircraft
(or aerostat) systems to greatly extend each ship’s en-
gagement horizon.
SM-2
Intercept
Kokee site A
RSTER
MK 74
Figure 7. Data reduction plot of tracks from the first beyond-the-
horizon firing. The track histories of the drone and the intercepting
missile are shown. The histories terminate at the intercept point
where the missile impacts the drone. As the engagement is
ordered by the ship, the MK 74 automatically is cued from the
RSTER data and acquires the target. MK 74 data are used for
missile guidance via the ship.
RSTER
MK 74
SM-2
Kokee site A
Intercept
Figure 8. Data reduction plot of tracks from the second beyond-
the-horizon firing (see Fig. 7 caption).

Phase 2: Army Experiments
The Army was unprepared as of 1996 to conduct
firing tests comparable to those of the Navy. Their plan,
therefore, called for simulated engagements and captive
seeker experiments to test the potential of forward pass
intercepts by a Patriot weapon system. Elements of
the simulations and experiments were the Patriot
PAC-3 weapon system located at Barking Sands (Fig. 5),
a computer simulation of the missile, and the aircraft-
mounted advanced Patriot Extended-Range Intercept
Technology Missile (ERINT) captive seeker carried
aboard a C-130 aircraft to simulate target engagements
against low- to mid-altitude drones.
For this phase, the CEC composite track data were
transmitted from the Kokee site to the Patriot via a
JTIDS communications link using a “link all-purpose
workstation” interface unit to translate CEC messages
to JTIDS format. From Patriot, the composite data were
supplied to the simulation and linked to the captive
ERINT seeker.
These Army simulations were successful, demonstrat-
ing that the target would have been intercepted in a high
percentage of cases.6
For each ERINT seeker test, the
Patriot unit was able to cue the captive seeker to acquire
the target on the basis of CEC composite track data.
ENHANCED SCENARIOS
For Set 2 of the Mountain Top ACTD operations,
Enhanced Scenarios, two additional CEC-equipped
cruisers from the Atlantic Fleet and a CEC-equipped
U.S. Customs Service P-3 aircraft were brought in to
provide greater opportunities for joint, extended air
defense experimentation. With participation by an Air
Force AWACS test aircraft, a total of three Aegis ships
equipped with CEC, a Marine Corps Hawk system
(modified to accept fire control cues via CEC from
Aegis and mountain sensors), the P-3, and an Army
Patriot site, a truly all-service experiment under care-
fully controlled test conditions was made possible.
During this stage of Mountain Top tests, the Navy and
APL worked closely to establish the test objectives and
design and certify the scenarios, which were subse-
quently agreed to by the other services. Those objec-
tives aimed
• To provide further risk reduction opportunities for
the upcoming CEC initial operational capability
(IOC), i.e., formal Fleet deployment, later that year
• To provide an opportunity for further CEC data
collection in support of new tactics development and
new concepts
• To afford an opportunity for joint-services participa-
tioninalittoralsettingwithexplorationofsensorand
weapons networking (via CEC) and command/
control networking (via JTIDS)
Sequence of Operational Scenarios
Again, the Enhanced Scenarios comprised three phases:
1. Arrival on the scene: Aegis ships—the Cape St.
George, Lake Erie, and Anzio—and the Customs
Service P-3 equipped with CEC arrived on the scene
(Fig. 9a). The CEC network established a composite
area picture.
2. Defense against shore-based attack: the Army’s Pa-
triot battery and the Air Force’s AWACS joined
operations (Fig. 9b). Simulated air attacks were
launched against forces.
3. Jointlittoraloperations:Joint-serviceoperationswith
participation of the Navy ships, P-3, Patriot, Hawk,
AWACS, and fighters (Fig. 9c). Enemy jammers
attacked nearly all radars.
Phase 1: Arrival on the Scene
This initial phase featured two experiments that were
designed to provide data to support the development of
Figure 9. Enhanced scenarios: (a) Phase 1, arrival on the scene;
(b) phase 2, defense against shore-based attack; (c) phase 3, joint
littoral operations.
P-3
USS Lake Erie
USS Anzio
SPS-48E
F-16s F-16s
Radar
sectors
(a)
Patriot
Drones
P-3
AWACS
Jammer
Silent shooter
target
(b)
AWACS
Patriot
F-16s/15s
F-15s or C-12s
F-16s/15s
F-16s
P-3
Jammers
USS Lake Erie
USS Anzio
Hawk
TSP-59/
fire
control
(c)
USS Cape
St. George
USS Cape
St. George
Kokee
Kokee
Kokee

advanced CEC functions. The first experiment involved
the three Aegis cruisers, the Kokee site, and the P-3
aircraft in the CEC network. Its objective was to collect
data relevant to the ability of CEC to allow radar cov-
erage coordination. In severe clutter or jamming or
against difficult targets (e.g., future tactical ballistic
missiles), units equipped with CEC may each elect to
cover only certain sectors with their radars to cooper-
atively manage available transmitter energy and retain
appropriately short search frame times. These sectors
may be coordinated via CEC. In that case, if a unit
detects a target in its sector, the other ships’ radars may
cue off the data, or one of the other ships may even
engage the target using the detecting unit’s data (i.e., an
EOR). The data collected in these tests indicated that
the units were effectively positioned to uncover regions
blocked by terrain. Thus, although several tracks were
only held by certain units at a time (because of blockage,
sectoring, etc.), CEC allowed all networked components
to process the collection of radar measurement data from
all other CEC units with accuracy comparable to or
better than the sensors themselves. As tracks transi-
tioned between sensors, composite track continuity (in
terms of position, velocity, identification, and composite
track number) was maintained.
The second set of experiments in Phase 1 was per-
formed to collect data for laboratory testing of a new
capability that was introduced in CEC for its IOC that
occurred later in 1996. This capability integrates radar
passive angle (PAT) data from targets emitting radia-
tion in the radar band into the CEC composite tracking
process. The new algorithms associate PAT measure-
ments with CEC track data and associate PAT data
from two or more units to derive range and bearing as
well as elevation angles as outputs of the CEC filter
(analogous to passive range triangulation). A “deghost-
ing” algorithm also acts to resolve multiple jammers to
obtain a unique aircraft location of each or an indica-
tion that insufficient data are available to do so. Con-
firming previous analyses, the radar passive range com-
posite track was of sufficient quality that it could
support missile engagements over a wide range of
emitting target positions relative to the tracking ships.
This capability for missile engagements from passive
composite track data is planned for future incorpora-
tion into CEC and Aegis.
Despite test curtailment due to extremely severe
weather, some very useful data were collected, allowing
laboratory evaluation of the real-time passive tracking
process. The data supported both PAT-to-active track
association and passive ranging, as shown in Fig. 10. The
IOC package did, in fact, successfully field the new CEC
passive range tracking capability. In addition, data col-
lections from all units were obtained to support further
CEC and JTIDS network architecture assessment.
Passive
only track
Radiating aircraft 1
Passive/
active
track
Radiating aircraft 2
Active track
Figure 10. Passive ranging scenario. Shown are the track histories
from two separate aircraft emitting radiation in the radar band for
which the cruisers each obtain a passive angle track (without the
range dimension). The data collected from the passive ranging
scenario were replayed through the next-generation Cooperative
Engagement Processor tracker several weeks after the event to
confirm the process for the subsequent CEC initial operational
capability (IOC). The CEC IOC track filter used active (three-
dimensional) and passive (two-dimensional) track measurement
datatogeneratehighlyaccuratethree-dimensionalcompositetracks.
Phase 2: Defense Against Shore-Based Attack
These scenarios consisted of several simulated and
actual missile engagements. The first event demonstrat-
ed the ability of CEC to provide high-quality composite
tracks in the presence of various forms of electronic
countermeasures against the networked sensors.
The second scenario demonstrated CEC’s ability to
support the Navy’s “silent shooter” tactic. In this tac-
tic, one or more ships are stationed at positions that
give them good engagement coverage of regions
where hostile missiles or aircraft might attempt to
penetrate. These ships operate in an “emissions con-
trol” state with radiating systems off (at least in the
expected penetration sector). They are linked by the
CEC network to ships with active radar located where
they could only be reached by hostile forces if they
flew through the area guarded by the silent units. A
silent ship, knowing the enemy’s precise location via
the CEC network, could launch an SM-2 missile to
engage the target, without ever enabling radar search,
using remote data from the network to direct
midcourse guidance and target illumination. If the
engagement could be completed before the firing
ship could be detected, a very effective silent
shooter capability would result. The simulated en-
gagements by the “silent” ship in this scenario provid-
ed valuable data for future system design and tactics
development.

Two missile firing scenarios were also executed
during this phase. To increase range safety margins for
the multiple ships participating, drone targets operated
at altitudes above those used in the beyond-the-hori-
zon tests. Instrumented SM-2 Block III missiles were
used. In one scenario, BQM-34 drones were flown
simultaneously at two cruisers, with a third cruiser off
to the side. The objectives of this scenario were two-
fold: (1) to provide two simultaneous engagements on
remote data with the same remote data source (for the
first time), and (2) to collect data for a risk reduction
evaluation of a new coordinated engagement algo-
rithm known as “first launch” (invented by the Aegis
prime contractor, Lockheed Martin, while under APL
subcontract in the mid-1980s).
The first launch process was incorporated in the
CEC IOC package in 1996. When enabled by an
operator, this feature allows the first ship to order an
engagement to report over CEC, so that the other ship
removes the target from its immediate engagement
queue, thereby minimizing unwanted, redundant en-
gagements. The test event culminated with successful
launches and engagements by the Anzio and Cape St.
George using remote data from the Lake Erie. The
engagements were so well coordinated by the firing
ships that the intercepts occurred nearly simulta-
neously. Figure 11 is a snapshot of the CEC display
of the event during the midcourse phase of the
engagement.
In a similar firing scenario, the Anzio engaged
and successfully intercepted a pair of targets using re-
mote data from the Lake Erie. This was the first occur-
rence of multiple engagements by a firing ship using
remote data and was scored as a success (Fig. 12).
In all, there were five successful SM-2 Block III
EOR firings.
Figure 11. CEC snapshot of dual cooperative engagement events by two firing ships—the USS Anzio (CG 68) and Cape St. George (CG
71)—engaging drones using the USS Lake Erie (CG 70) SPY-1B remote data. The triangles are the drone targets. The CEC-equipped
units are circles. The upper-half squares near the drones are SMs in flight.The dotted lines between CG 70 and the targets indicate that
CG 70 is the source of fire control data. The solid lines between CG 68 and 71 and the drones indicate the target/ship engagement pairings.
The thin solid lines indicate direct CEC connectivity among CEC units.

Figure 12. CEC data reduction plot of dual drone cooperative engagements by a single
ship. The track histories of the drones were obtained by the USS Lake Erie (CG 70), which
was the source for dual engagements on remote data by the Anzio (CG 68).
Phase 3: Joint Littoral Operations
This final phase of the Enhanced Scenarios provided
an opportunity for the CEC-equipped ships, P-3 air-
craft, and the Kokee site to operate with joint elements
in a common scenario. The Navy units were intercon-
nected by the CEC and to the Army and Air Force by
the JTIDS. The first all-services operations using a
tactical Model 4 JTIDS network were conducted.
AWACS radar data were collected in these operation-
ally representative situations simultaneously with CEC
network data as a basis for beginning development of
requirements and a design concept for integration of
AWACS into the CEC network. TPS-59 radar data
were collected for the same purpose. Development work
using these data has begun. The CEC network tracks
of several “two-on-two” F-15/ 16 air combat operations
were conducted. These composite tracks were formed
by the radar and IFF equipment on the three Aegis
cruisers and the P-3, with no loss of track identity or
continuity, even though significant main-beam radar
jamming was present.
The primary scenario consisted of 12 fighters, half
designated blue force and half red force, to conduct
operations in concert with airborne electronic counter-
measures against participating radars. It was first run with
the CEC operating using a specially defined composite
identification doctrine and CEC
tracks reported over JTIDS only
from the Kokee site JTIDS unit
(others were in a receive-only con-
dition) to represent the near-future
CEC/JTIDS interoperability archi-
tecture. This architecture will fea-
ture CEC sensor-networked identi-
fication doctrine in accordance
with JTIDS-promulgated com-
mand/control doctrine as well as
JTIDS reporting of CEC composite
tracks for greater track life and
more consistent track number and
identification correlation. Figure
13 is a data reduction plot of the
event midway through the scenar-
io. A second “without CEC” run of
this same scenario allowed the
units to operate the first truly joint
JTIDS Link 16 protocols with the
three cruisers, AWACS, and Patri-
ot in the network.
Also as part of this phase, the
Hawk battery conducted live firings
against drones. The scenario con-
sisted of a BQM-74 drone with
towed targets inbound toward the
battery. For one firing, the compos-
ite track data were supplied by CEC
and relayed through the aerostat, mentioned earlier,
using a single-channel ground-to-air military radio as a
surrogate CEC Data Distribution System (see the boxed
insert). The composite track consisted of sensor data
from the three Aegis cruisers and the Kokee site. Figure
14 illustrates the configuration. All five Hawk engage-
ments were successfully executed with either fire control
radar cues from CEC or from the TPS-59 radar on
Makaha Ridge (representing an elevated sensor).
As part of the follow-on evaluation, collected TPS-59
data have since been processed through a CEC processor
at APL and integrated into the composite track picture.
Figure 15 is a CEC display snapshot of the composite
track history for data collected during one of the Hawk
missile firings. The resulting composite track picture,
although not fully optimized to specification at that time,
revealed the potential contribution of such a land-based
radar to the Navy CEC network. From its elevated van-
tage point, the TPS-59 provided radar data of a target not
detected by the other CEC units as well as early detection
of the drone launch from Barking Sands. The latter would
have provided for automatic special acquisition of the
target by one of the Aegis radars if the TPS-59 had
actually been in the CEC network. These results were an
initial step toward the integration of the TPS-59 radar
and CEC, which was achieved in 1997.
Jammer
aircraft
Outbound
drones
Inbound drones
Missile track
Kokee site ACG 68
CG 70
CG 71
AWACS track

Figure 13. CEC data reduction plot of a complex joint operations
scenario. The composite track histories of the scenario are shown.
Tracking and identification continuity were maintained throughout,
and the CEC composite tracks were reported over JTIDS from the
Kokee site. The colors in the track histories correspond to the
colors of the CEC units indicating the portions of the track contrib-
uted by each unit.
Figure 14. Illustrated configuration of Aegis, CEC, aerostat, and Hawk. The Hawk high-powered illuminator/tracking radar was cued for
successful engagements from the TPS-59 radar at the elevated Makaha site, as well as from the Aegis cruisers via CEC composite track.
Three data paths are shown: blue, Aegis SPY composite CEC track via aerostat relay to cue Hawk fire control; yellow, cue of TPS radar
and radar cue of Hawk fire control; red, direct cue of Hawk fire control.
Results
This portion of Mountain Top also met, and in
several cases exceeded, its primary objectives. For ex-
ample, it demonstrated the capability of CEC to sup-
port the Navy’s silent shooter concept. In addition, two
simultaneous ship engagements with SM-2 using re-
mote data were successfully accomplished for the first
time. The exercise provided an unprecedented oppor-
tunity for concept exploration and data collection with
five CEC-equipped units (three of which were Navy
cruisers) operating with the participation of the Army,
Marine Corps, and Air Force elements in a series of
littoral scenarios. It supplied invaluable data for eval-
uation of the potential integration of AWACS and
the Marine Corps’ TPS-59 Hawk radar into the CEC
network.
SUMMARY
Significance of Test Results
The Mountain Top ACTD successfully demonstrat-
ed the feasibility of the forward pass mode of target
engagement, an approach conceived over 20 years ago
to extend air defense capability beyond a ship’s horizon
USAF
AWACS and
KC-135
tanker
CG 68
CG 71
CG 70
Kokee
site A
F-16s (2)
F-15s (4)
Jammer
Jammer
Jammer
Jammer
P-3
CG 71
CG 68
Target
TPS-59
CEC
Kokee site
CEC
line
Hawk launchers
and fire control/
illuminators
Aerostat relay
of CEC data
TPS-59 data
fiber-optic line
Makaha Ridge
Hawk/CEC experimental
fire control interface
CEC network
Aegis firm track
of target

Makaha
Composite track
with TPS-59 and Aegis
SPY-1 contribution
Composite track
from TPS-59 data only
CG 71
CG 68
TPS-59
Figure 15. CEC display with TPS-59 radar. A replay of collected TPS-59 radar measure-
ments, conditioned to appear in the format of an SPS-48E radar, was run through a
Cooperative Engagement Processor along with data collected simultaneously from CEC
units. The lower track indicates that the TPS-59 had detected a target not detected by the
cruisers. The track emerging and then turning toward the island is a target drone. The TPS-
59wasinapositiontodetecttheoutboundtargetbeforetheCapeSt.George(CG71)could
do so. Had it been networked with the CEC, CG 71 could have provided data for the
cruiser’s SPY-1B to acquire the drone prior to its own autonomous detection.
with the aid of surveillance and target illumination air
vehicles.7
In his message of congratulations, the late
Chief of Naval Operations ADM Mike Boorda wrote
‘Outstanding’ is the only word to describe the re-
sounding success you all achieved in both the advanced
concept technology demonstration (ACTD) and en-
hanced phases of the recently completed Mountain Top
demonstrations. In discussing emerging technologies
and warfighting capabilities, ‘revolutionary’ may be one
of the most overused words in Washington. In this case,
however, there is no question that you have set the stage
for a revolutionary new way of fighting in the air defense
arena. Because of your dedication and hard work, our
task of quickly deploying this unprecedented warfighting
capability has been made much easier. You were on time,
on target, and on the money. Congratulations on a major
success. All the best.8
The evolution of the concept and the ability of ex-
isting Navy systems to be modified for such a demonstra-
tion were the result of convergent mutual development
of these systems, with APL as a key player. The fact that
CEC, conceived by APL, was designed to enable such
forms of cooperative engagement is due to the Labora-
tory’s capability to preserve the technical vision over
multiple generations. It may also be attributed to APL’s
complementary roles in development of Navy air defense
systems that enable it, in partnership with the Navy, to
ensure that key synergistic features
are present in these systems to facil-
itate their technical advance in a
balanced, focused, and mutually sup-
porting manner.
The potential of the land-attack
CMD concept to protect U.S. and
coalition forces in future conflicts is
a compelling reason for further de-
velopment of such capabilities by
the joint services. The success of
the Mountain Top exercises pro-
vided a critical step toward this ob-
jective by proving the integration
concept and the potential perfor-
mance amplification over individ-
ual systems. These tests also further
explored the foundations of weap-
on and sensor networking (via
CEC) and command/control net-
working (via JTIDS) for joint-ser-
vices CMD operations.
The Future
Since the Mountain Top be-
yond-the-horizon firing events
were successfully completed, dis-
cussions of a follow-on have been
intense. The definition of the follow-on CMD phase
is being vigorously pursued by DoD, with all services
recommending roles and next-phase approaches. As of
this writing, a substantial test operation, even exceed-
ing Set 1 in scale, is being discussed, with the intent
to lead to a deployable prototype national resource.
The various airborne platform options under consid-
eration include a very large Army aerostat, a large Air
Force aircraft, and a Navy carrier aircraft, possibly with
unmanned aerial vehicles in a CEC subnet for en-
hanced performance. Advanced Army, Navy, and Air
Force missile variants are also being considered, and
CEC and JTIDS are expected to be integrated as the
sensor/weapons network and command/control net-
work, respectively.
The Enhanced Scenarios also have made an impact.
First, they contributed to CEC meeting its congression-
ally directed IOC schedule, with significant risk reduc-
tion having been part of those scenarios. Second, the
Marine Corps has begun integrating CEC into its Hawk
system, and the Air Force and Army are considering
prototype integrations of CEC into the AWACS test
aircraft and missile batteries, respectively. All the ser-
vices are further examining the use of CEC and JTIDS
for CMD as well as tactical ballistic missile defense roles
in a joint networking study.

THE AUTHORS
JERRY A. KRILL received his B.S. and M.S. degrees from Michigan State
University in 1973 and 1974, respectively, and a Ph.D. from the University of
Maryland in 1978, all in electrical engineering. In 1973 he joined the
Laboratory, where he is presently Supervisor of the Sensor and Weapon Control
Engineering Branch of the Air Defense Systems Department. He is also a
lecturer for The Johns Hopkins University Part-Time Graduate Program.
Originally specializing in electromagnetic theory, Dr. Krill has published articles
on electromagnetic scattering and guided wave technology and holds a number
of U.S. patents. He has led systems engineering and critical experiments for the
Navy’s Aegis and Battle Group Anti-Air Warfare Coordination programs. For 10
years he served as the APL System Engineer for the Cooperative Engagement
Capability. Dr. Krill was recently named APL’s lead System Concept Engineer
for the Navy Program Executive Office for Theater Air Defense. His e-mail
address is Jerry.Krill@jhuapl.edu.
WILLIAM H. ZINGER is a member of APL’s Principal Professional Staff and
Associate Head of the Air Defense Systems Department. He obtained a B.S.E.E.
from the University of Pennsylvania in 1961. Since joining APL in 1962, Mr.
Zinger has worked on the design and testing of Fleet radars and related
electronics. He has been associated with Aegis and its AN/SPY-1 radar since
program inception. More recently, he served as the Technical Director of APL’s
Cooperative Engagement Capability effort and led the Ship Self-Defense System
effort within his organization. His e-mail address is William.Zinger@jhuapl.edu.
REFERENCES
1“The Cooperative Engagement Capability,” Johns Hopkins APL Tech. Dig.
16(4), 377–396 (1995).
2Cruise Missile Defense Advanced Concept Technology Demonstration Phase I,
Office of Naval Research (Mountain Top) ACTD Management Plan (Aug
1994).
3Dockery, G. D., and Konstanzer, G. C., “Recent Advances in Prediction of
Tropospheric Propagation Using the Parabolic Equation,” Johns Hopkins APL
Tech. Dig. 8(4), 404–412 (1987).
4Rowland, J. R., and Babin, S. M., “Fine-Scale Measurements of Microwave
Refractivity Profiles with Helicopter and Low-Cost Rocket Probes,” Johns
Hopkins APL Tech. Dig. 8(4), 413–417 (1987).
5Marcotte, F. J., and Hanson, J. M., “An Airborne Captive Seeker with Real-
Time Analysis Capability,” Johns Hopkins APL Tech. Dig. 18(3), 422–431
(1997).
6Moore, D., 1996 National Fire Control Symposium, Eglin Air Force Base (Jul–
Aug 1996).
7Blazar, E., “Firing Blind, Not Blindly,” Navy Times (29 Jan 1996).
8Boorda, M., “SUBJ/BRAVO ZULU//” Navy Message from CNO, N03210,
MSGID/GENADMIN/CNO(N86)//Washington, DC (23 Mar 1996).
ACKNOWLEDGMENTS: The authors wish to thank Alexander Kossiakoff,
APL Director Emeritus, for his valued editorial guidance in preparing this manu-
script. We also gratefully acknowledge the leadership provided by the Mountain
Top ACTD and CEC program manager, Michael J. O’Driscoll, whose insight,
team-building, issues resolution capabilities, and adherence to the systems engi-
neering process were critical in making Mountain Top an unqualified success.

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